Organic electroluminescent device material and organic electroluminescent device using same

ABSTRACT

A material for organic electroluminescence devices comprising a compound having a specific condensed cyclic structure having nitrogen atom and an organic electroluminescence device comprising an organic thin film layer which comprises at least one layer and is sandwiched between an anode and a cathode, wherein at least one of the layers in the organic thin film layer contains the above material, are provided. The organic electroluminescence device utilizes emission of phosphorescent light, exhibits a great current efficiency and has a long lifetime.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent(“electroluminescent” and “electroluminescence” will be referred to as“EL”, hereinafter) device material and an organic EL device using thesame. More particularly, the present invention relates to a material fororganic EL devices which utilizes emission of phosphorescent light,exhibits a great current efficiency and has a long lifetime and anorganic EL device using the material.

BACKGROUND ART

An organic EL device is a spontaneous light emitting device whichutilizes the principle that a fluorescent substance emits light byenergy of recombination of holes injected from an anode and electronsinjected from a cathode when an electric field is applied. Since anorganic EL device of the laminate type driven under a low electricvoltage was reported by C. W. Tang of Eastman Kodak Company (C. W. Tangand S. A. Vanslyke, Applied Physics Letters, Volume 51, Pages 913,1987), many studies have been conducted on organic EL devices usingorganic materials as the constituting materials. Tang et al. used alaminate structure using tris(8-hydroxyquinolinol)aluminum for the lightemitting layer and a triphenyldiamine derivative for the holetransporting layer. Advantages of the laminate structure are that theefficiency of hole injection into the light emitting layer can beincreased, that the efficiency of forming excited particles which areformed by blocking and recombining electrons injected from the cathodecan be increased, and that excited particles formed within the lightemitting layer can be enclosed. As the structure of the organic ELdevice, a two-layered structure having a hole transporting (injecting)layer and an electron transporting and light emitting layer and athree-layered structure having a hole transporting (injecting) layer, alight emitting layer and an electron transporting (injecting) layer arewell known. To increase the efficiency of recombination of injectedholes and electrons in the devices of the laminate type, the structureof the device and the process for forming the device have been studied.

As the light emitting material of the organic EL device, chelatecomplexes such as tris(8-quinolinolato)aluminum, coumarine derivatives,tetraphenylbutadiene derivatives, bisstyrylarylene derivatives andoxadiazole derivatives are known. It is reported that light in thevisible region ranging from blue light to red light can be obtained byusing these light emitting materials, and development of a deviceexhibiting color images is expected (refer to, for example, JapanesePatent Application Laid-Open Nos. Heisei 8(1996)-239655, Heisei7(1995)-138561 and Heisei 3(1991)-200289).

It is recently proposed that an organic phosphorescent materials is usedin the light emitting layer of an organic EL device in combination witha light emitting material (for example, D. F. O'Brien, M. A. Baldo etal., “Improved energy transfer in electrophosphorescent devices”,Applied Physics Letters, Vol. 74, No. 3, Pages 442 to 444, Jan. 18,1999; and M. A. Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence”, Applied PhysicsLetters, Vol. 75, No. 1, Pages 4 to 6, Jul. 5, 1999).

As described above, a great efficiency of light emission is achieved byutilizing an organic phosphorescent material excited to the singletstate and the triplet state in the light emitting layer of an organic ELdevice. It is considered that singlet excimers and triplet excimers areformed in relative amounts of 1:3 due to the difference in themultiplicity of spin when electrons and holes are recombined in anorganic EL device. Therefore, it is expected that an efficiency of lightemission 3 to 4 times as great as that of a device utilizingfluorescence alone can be achieved by utilizing a material emittingphosphorescent light.

The organic EL device utilizing phosphorescent light emission is stillunder study, and an organic EL device exhibiting a great efficiency oflight emssion and having a long lifetime is also being studied. As oneof such studies, a device containing a phosphorescent emissive compoundin the light emitting layer and emitting turquoise light at an externalquantum efficiency of 10% is disclosed in Japanese Patent ApplicationLaid-Open No. 2002-100476. However, neither the efficiency of lightemission nor the luminance of the device is mentioned in thespecification of Japanese Patent Application Laid-Open No. 2002-100476,and it is not known whether the device has the properties useful forpractical applications. Therefore, an organic EL device utilizing thephosphorescent light emission which exhibits an efficiency of lightemission and a lifetime sufficient for practical applications has beendesired.

DISCLOSURE OF THE INVENTION

The present invention has been made to overcome the above problems andhas an object of providing an organic EL device which utilizesphosphorescent light emission, exhibits a great current efficiency andhas a long lifetime.

As the result of extensive studies by the present inventors to achievethe above object, it was found that an organic EL device which utilizedphosphorescent light emission, exhibited a great efficiency of lightemission and had a long lifetime could be obtained by using a compoundhaving a specific condensed cyclic structure having nitrogen atom. Thepresent invention has been completed based on this knowledge.

The present invention provides a material for organic EL devices whichcomprises a compound represented by following general formula (1):

wherein X₁ to X₈ each represent carbon atom or nitrogen atom, and atleast one of X₁ to X₈ represents nitrogen atom; when any of X₁ to X₈represent carbon atom, R₁ to R₈ connected to X₁ to X₈ representingcarbon atom, respectively, each represent a substituent bonded to thecarbon atom, respectively, each represent a substituent bonded to thecarbon atom; adjacent substituents represented by R₁ to R₈ may form aring; when any of X₁ to X₈ represent nitrogen atom, R₁ to R₈ connectedto X₁ to X₈ representing nitrogen atom, respectively, each represent anoncovalent electron pair; and R₉ represents a substituent.

The present invention also provides an organic EL device comprising acathode, an anode and an organic thin film layer which is sandwichedbetween the cathode and the anode and comprises at least one layer,wherein at least one layer in the organic thin film layer contains amaterial for organic EL devices described above. It is preferable that alight emitting layer, an electron transporting layer and/or an electroninjecting layer or a hole transporting layer and/or a hole injectinglayer contains the above material for organic EL devices.

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

The material for organic electroluminescence devices of the presentinvention comprises a compound represented by following general formula(1):

In the above formula (1), X₁ to X₈ each represent carbon atom ornitrogen atom, and at least one of X₁ to X₈ represents nitrogen atom.When any of X₁ to X₈ represent carbon atom, R₁ to R₈ connected to X₁ toX₈ representing carbon atom, respectively, each represent a substituentbonded to the carbon atom. Adjacent substituents represented by R₁ to R₈may form a ring. When any of X₁ to X₈ represent nitrogen atom, R₁ to R₈connected to X₁ to X₈ representing nitrogen atom, respectively, eachrepresent a noncovalent electron pair. R₉ represents a substituent.

The substituents represented by R₁ to R₉ may each represent -L or -L-Y,in which L is directly connected to X₁ to X₈ (in the case of R₁ to R₈)or to N (in the case of R₉).

L represents hydrogen atom, a substituted or unsubstituted aryl grouphaving 6 to 40 carbon atoms, a substituted or unsubstituted heterocyclicgroup having 2 to 40 carbon atoms, a substituted or unsubstituted linearor branched alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted cycloalkyl group having 6 to 40 carbon atoms, asubstituted or unsubstituted amino group having 2 to 40 carbon atoms, asubstituted or unsubstituted linear or branched alkoxyl group having 1to 40 carbon atoms, a halogen atom, nitro group, a substituted orunsubstituted arylene group having 6 to 40 carbon atoms, a substitutedor unsubstituted divalent heterocyclic group having 2 to 40 carbonatoms, a linear or branched substituted or unsubstituted alkylene grouphaving 1 to 20 carbon atoms or a substituted or unsubstitutedcycloalkylene group having 6 to 40 carbon atoms.

Y represents hydrogen atom, a substituted or unsubstituted aryl grouphaving 6 to 40 carbon atoms, a substituted or unsubstituted heterocyclicgroup having 2 to 40 carbon atoms, a substituted or unsubstituted linearor branched alkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted cycloalkyl group having 6 to 40 carbon atoms, asubstituted or unsubstituted amino group having 2 to 40 carbon atoms, asubstituted or unsubstituted linear or branched alkoxyl group having 1to 40 carbon atoms, a halogen atom or nitro group.

Examples of the aryl group represented by L include phenyl group,1-naphthyl group, 2-naphthyl group, 1-anthryl group, 2-anthryl group,9-anthryl group, 1-phenanthryl group, 2-phenanthryl group, 3-phenanthrylgroup, 4-phenanthryl group, 9-phenanthryl group, 1-naphthacenyl group,2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl group, 2-pyrenylgroup, 4-pyrenyl group, 2-biphenylyl group, 3-biphenylyl group,4-biphenylyl group, p-terphenyl-4-yl group, p-terphenyl-3-yl group,p-terphenyl-2-yl group, m-terphenyl-4-yl group, m-terphenyl-3-yl group,m-terphenyl-2-yl group, o-tolyl group, m-tolyl group, p-tolyl group,p-t-butylphenyl group, p-(2-phenylpropyl)phenyl group,3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group, 4-methyl-1-anthrylgroup, 4′-methylbiphenylyl group, 4″-t-butyl-p-terphenyl-4-yl group,fluorenyl group and perfluoroaryl groups.

Examples of the alkyl group represented by L include methyl group,trifluoromethyl group, ethyl group, propyl group, isopropyl group,n-butyl group, s-butyl group, isobutyl group, t-butyl group, n-pentylgroup, n-hexyl group, n-heptyl group, n-octyl group, hydroxymethylgroup, 1-hydroxyethyl group, 2-hydroxyethyl group, 2-hydroxyisobutylgroup, 1,2-dihydroxyethyl group, 1,3-dihydroxyisopropyl group,2,3-dihydroxy-t-butyl group, 1,2,3-trihydroxypropyl group, chloromethylgroup, 1-chloroethyl group, 2-chloroethyl group, 2-chloroisobutyl group,1,2-dichloroethyl group, 1,3-dichloroisopropyl group,2,3-dichloro-t-butyl group, 1,2,3-trichloropropyl group, bromomethylgroup, 1-bromoethyl group, 2-bromoethyl group, 2-bromoisobutyl group,1,2-dibromoethyl group, 1,3-dibromoisopropyl group, 2,3-dibromo-t-butylgroup, 1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group,2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group,1,3-diiodoisopropyl group, 2,3-diiodo-t-butyl group, 1,2,3-triiodopropylgroup, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group,2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropylgroup, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group,cyanomethyl group, 1-cyanoethyl group, 2-cyanoethyl group,2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropylgroup, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl group,nitromethyl group, 1-nitroethyl group, 2-nitroethyl group,2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropylgroup, 2,3-dinitro-t-butyl group and 1,2,3-trinitropropyl group.

As for the substituted aryl group, when, for example, phenyl grouphaving 6 carbon atoms is substituted with a substituent such as phenylgroup and methyl group, examples of the substituted aryl group includegroups having the following structures:

Examples of the cycloalkyl group represented by L include cyclopentylgroup, cyclohexyl group, 4-methylcyclohexyl group, adamantyl group andnorbornyl group.

Example of the amino group represented by L include dimethylamino group,methylethylamino group, diphenylamino group, diisopropylamine group,bis-diphenylamino group, carbazolyl group, diethylamino group,ditolylamino group, indolyl group, piperidyl group and pyrrolidinylgroup.

The alkoxyl group represented by L is represented by —OY¹. Examples ofthe group represented by Y¹ include methyl group, trifluoromethyl group,ethyl group, propyl group, isopropyl group, n-butyl group, s-butylgroup, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group,n-heptyl group, n-octyl group, hydroxymethyl group, 1-hydroxyethylgroup, 2-hydroxyethyl group, 2-hydroxyisobutyl group, 1,2-dihydroxyethylgroup, 1,3-dihydroxy-isopropyl group, 2,3-dihydroxy-t-butyl group,1,2,3-trihydroxypropyl group, chloromethyl group, 1-chloroethyl group,2-chloroethyl group, 2-chloroisobutyl group, 1,2-dichloroethyl group,1,3-dichloroisopropyl group, 2,3-dichloro-t-butyl group,1,2,3-trichloropropyl group, bromomethyl group, 1-bromoethyl group,2-bromoethyl group, 2-bromoisobutyl group, 1,2-dibromoethyl group,1,3-dibromoisopropyl group, 2,3-dibromo-t-butyl group,1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group,2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group,1,3-diiodoisopropyl group, 2,3-diiodo-t-butyl group, 1,2,3-triiodopropylgroup, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group,2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropylgroup, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group,cyanomethyl group, 1-cyanoethyl group, 2-cyanoethyl group,2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropylgroup, 2,3-dicyano-t-butyl group, 1,2,3-tricyano-propyl group,nitromethyl group, 1-nitroethyl group, 2-nitroethyl group,2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropylgroup, 2,3-dinitro-t-butyl group and 1,2,3-trinitropropyl group.

Examples of the halogen atom represented by L include fluorine atom,chlorine atom, bromine atom and iodine atom.

Examples of the arylene group represented by L include divalent groupsderived from the groups described above as the examples of the arylgroup represented by L.

As for the substituted aryl group, when, for example, phenyl grouphaving 6 carbon atoms is substituted with a substituent such as phenylgroup and methyl group, examples of the substituted aryl group includegroups having the following structures:

Examples of the substituted or unsubstituted divalent heterocyclic grouphaving 2 to 40 carbon atoms which is represented by L include divalentgroups derived from the groups described above as the examples of theheterocyclic group represented by L.

Examples of the alkylene group represented by L include divalent groupsderived from the groups described above as the examples of the alkylgroup represented by L.

Examples of the cycloalkylene group represented by L include divalentgroups derived from the groups described above as the examples of thecycloalkyl group represented by L.

Examples of the aryl group, the heterocyclic group, the alkyl group, thecycloalkyl group, the amino group, the alkoxyl group and the halogengroup represented by Y include the groups described above as theexamples of the corresponding groups represented by L.

It is preferable that, in general formula (1), one to three among X₁ toX₈ each represent nitrogen atom, and the others each represent carbonatom. It is more preferable that X₃ and/or X₆ represents nitrogen atom,and the others each represent carbon atom.

It is still more preferable that at least one of R₁ to R₈ representsβ-carbolinyl group. In other words, L and/or Y represents β-carbolinylgroup.

Examples of the group substituting hydrogen atom on the atomsrepresented by X₁ to X₈ and in the substituents represented by R₁ to R₉include halogen atoms such as fluorine atom, chlorine atom and bromineatom, cyano group, silyl group, amino group, aryl groups, aryloxylgroups, heterocyclic group, alkyl groups, alkoxyl groups, aralkyl groupsand cycloalkyl groups.

Examples of the compound represented by general formula (1) comprised inthe material for organic EL devices of the present invention are shownin the following. However, the material of the present invention is notlimited to the compounds shown as the examples.

It is preferable that the material for organic EL devices of the presentinvention comprising the compound represented by general formula (1) hasan energy gap of the triplet state of 2.5 to 3.3 eV and more preferably2.6 to 3.2 eV.

It is preferable that the material for organic EL devices of the presentinvention comprising the compound represented by general formula (1) hasan energy gap of the singlet state of 2.8 to 3.8 eV and more preferably2.9 to 3.6 eV.

The organic EL device comprises a cathode, an anode and an organic thinfilm layer which is sandwiched between the cathode and the anode andcomprises at least one layer, and at least one layer in the organic thinfilm layer contains the material for organic EL devices comprising thematerial represented by general formula (1) described above.

It is preferable that the light emitting layer, the electrontransporting layer and/or the electron injecting layer or the holetransporting layer an/or the hole injecting layer in the organic ELdevice of the present invention contains the material for organic ELdevices comprising the material represented by general formula (1)described above.

It is preferable that the organic thin film layer in the organic ELdevice of the present invention contains a phosphorescent emissivecompound. As the phosphorescent emissive compound, metal complexesemitting light by a multiplet excitation which is the excitation to thetriplet state or higher are preferable. Examples of the metal complexinclude the following compounds:

It is preferable that the material for organic EL devices is a hostmaterial of the organic EL device. The host material is a material intowhich holes and electrons can be injected and which has the function oftransporting holes and electrons and emitting fluorescence byrecombination of holes and electrons.

The compound represented by general formula (1) in the present inventionis useful also as the organic host material for phosphorescence devicessince the energy gap of the singlet state is as great as 2.8 to 3.8 eVand the energy gap of the triplet state is as great as 2.5 to 3.3 eV.

The phosphorescence device is an organic device which comprises asubstance emitting light based on the transition from the energy levelin the triplet state to the energy level in the ground singlet statewith a stronger intensity than those emitted from other substances,examples of which include phosphorescent substances such asorganometallic complexes comprising at least one metal selected fromGroups 7 to 11 of the Periodic Table, and emits light under an electricfield utilizing the so-called phosphorescence.

In the light emitting layer of the organic EL device, in general, thesinglet exciton and the triplet exciton are contained in the formedexcited molecules as a mixture, and it is said that the triplet excitonis formed in a greater amount such that the ratio of the amount of thesinglet exciton to the amount of the triplet exciton is 1:3. Inconventional organic EL devices using the fluorescence, the excitoncontributing to the light emission is the singlet exciton, and thetriplet exciton does not emit light. Therefore, the triplet exciton isultimately consumed as heat, and the light is emitted by the singletexciton which is formed in a smaller amount. Therefore, in these organicEL devices, the energy transferred to the triplet exciton causes a greatloss in the energy generated by the recombination of holes andelectrons.

In contrast, it is considered that, by using the material of the presentinvention for the phosphorescence device, the efficiency of lightemission three times as great as that of a device using fluorescence canbe obtained since the triplet exciton can be used for the emission oflight. It is also considered that, when the compound of the presentinvention is used for the light emitting layer of the phosphorescencedevice, an excited triplet level in an energy state higher than theexcited triplet level of a phosphorescent organometallic complexcomprising a metal selected from the Group 7 to 11 of the Periodic Tablecontained in the layer, is achieved; the film having a more stable formis provided; the glass transition temperature is higher (Tg: 80 to 160°C.); holes and/or electrons are efficiently transported; the compound iselectrochemically and chemically stable; and the formation of impuritieswhich may work as a trap or cause loss in the light emission issuppressed during the preparation and the use.

The organic EL device of the present invention comprises, as describedabove, a cathode, an anode and an organic thin film layer comprising atleast one layer and sandwiched between the cathode and the anode. Whenthe organic thin film layer comprises a single layer, a light emittinglayer is formed between the anode and the cathode. The light emittinglayer contains a light emitting material and may further contain a holeinjecting material for transporting holes injected from the anode to thelight emitting material or an electron injecting material fortransporting electrons injected from the cathode to the light emittingmaterial. It is preferable that the light emitting material exhibits avery excellent quantum yield, has a great ability of transporting bothholes and electrons and forms a uniform thin layer. Examples of theorganic EL device of the multi-layer type include organic EL devicescomprising a laminate having a multi-layer structure such as (theanode/the hole injecting layer/the light emitting layer/the cathode),(the anode/the light emitting layer/the electron injecting layer/thecathode) and (the anode/the hole injecting layer/the light emittinglayer/the electron injecting layer/the cathode).

For the light emitting layer, in addition to the material comprising thecompound represented by general formula (1) of the present invention,conventional host materials, light emitting materials, doping materials,hole transporting materials and electron transporting materials andcombinations of these materials may be used in combination, wherenecessary. By using a multi-layer structure for the organic EL device,decreases in the luminance and the lifetime due to quenching can beprevented, and the luminance of emitted light and the efficiency oflight emission can be improved with other doping materials. By usingother doping materials contributing to the light emission of thephosphorescent light in combination, the luminance of emitted light andthe efficiency of light emission can be improved in comparison withthose of conventional devices.

In the organic EL device of the present invention, the hole transportinglayer, the light emitting layer and the electron transporting layer mayeach have a multi-layer structure. When the hole transporting layer hasa multi-layer structure, the layer into which holes are injected fromthe electrode is called the hole injecting layer, and the layer whichreceives holes from the hole injecting layer and transports holes to thelight emitting layer is called the hole transporting layer. Similarly,when the electron transporting layer has a multi-layer structure, thelayer into which electron are injected from the electrode is called theelectron injecting layer, and the layer which receives electrons fromthe electron injecting layer and transports electrons to the lightemitting layer is called the electron transporting layer. The layers areselected in accordance with various properties such as the energy levelsof the material, heat resistance and adhesion with the organic thin filmlayers and the metal electrodes.

In the organic EL device of the present invention, the electrontransporting layer and the hole transporting layer may contain thematerial for organic EL devices of the present invention which comprisesthe compound represented by general formula (1). The hole injectinglayer, the electron injecting layer and the hole barrier layer maycontain the material for organic EL devices of the present invention.The phosphorescent emissive compounds and the material for organic ELdevices of the present invention may be used together as a mixture.

Examples of the light emitting material and the host material which canbe used for the organic thin film layer in combination with the compoundrepresented by general formula (1) include anthracene, naphthalene,phenanthrene, pyrene, tetracene, coronen, chrysene, fluoresceine,perylene, phthaloperylene, naphthaloperylene, perynone, phthaloperynone,naphthaloperynone, diphenylbutadiene, tetraphenyl-butadiene, coumarine,oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, pyrazine,cyclopentadiene, metal complexes of quinoline, metal complexes ofaminoquinoline, metal complexes of benzoquinoline, imines,diphenyl-ethylene, vinylanthracene, diaminoanthracene, diaminocarbazole,pyrane, thiopyrane, polymethine, melocyanine, oxinoid compounds chelatedwith imidazole, quinacridone, rubrene, stilbene-based derivatives andfluorescent pigments. However, the light emitting material and the hostmaterial are not limited to the compounds described above.

As the hole injecting material, compounds which have the ability totransport holes, exhibit the excellent effect of receiving holesinjected from the anode and the excellent effect of injecting holes tothe light emitting layer or the light emitting material, preventtransfer of excitons formed in the light emitting layer to the electroninjecting layer or the electron injecting material and have theexcellent ability of forming a thin film, are preferable. Examples ofthe hole injecting compound include phthalocyanine derivatives,naphthalocyanine derivatives, porphyrin derivatives, oxazoles,oxadiazoles, triazoles, imidazoles, imidazolones, imidazolethiones,pyrazolines, pyrazolones, tetrahydroimidazoles, oxazoles, oxadiazoles,hydrazones, acylhydrazones, polyarylalkanes, stilbene, butadiene,triphenylamine of the benzidine type, triphenylamine of the styrylaminetype, triphenylamine of the diamine type, derivatives of the abovecompounds and macromolecular materials such as polyvinylcarbazoles,polysilanes and electrically conductive macromolecules. However, thehole injecting material is not limited to these materials.

Among these hole injecting materials, the more effective hole injectingmaterials are aromatic tertiary amine derivatives and phthalocyaninederivatives. Examples of the aromatic tertiary amine derivative includetriphenylamine, tritolylamine, tolyldiphenylamine,N,N′-diphenyl-N,N′-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine,N,N,N′,N′-(4-methylphenyl)-1,1′-phenyl-4,4′-diamine,N,N,N′,N′-(4-methyl-phenyl)-1,1′-biphenyl-4,4′-diamine,N,N′-diphenyl-N,N′-dinaphthyl-1,1′-biphenyl-4,4′-diamine,N,N′-(methylphenyl)-N,N′-(4-n-butylphenyl)-phenanthrene-9,10-diamine,N,N-bis(4-di-4-tolylaminophenyl)-4-phenyl-cyclohexane and oligomers andpolymers having the skeleton structure of these aromatic tertiaryamines. However, the aromatic tertiary amine is not limited to thesecompounds. Examples of the phthalocyanine (Pc) derivative includephthalocyanine derivatives and naphthalocyanine derivatives such asH₂Pc, CuPc, CoPc, NiPc, ZnPc, PdPc, FePc, MnPc, ClAlPc, ClGaPc, ClInPc,ClSnPc, Cl₂SiPc, (HO)AlPc, (HO)GaPc, VOPc, TiOPc, MoOPc and GaPc-O-GaPc.However the phthalocyanine derivative is not limited to these compounds.

As the electron injecting material, compounds which have the ability totransport electrons, exhibit the excellent effect of receiving electronsinjected from the anode and the excellent effect of injecting electronsto the light emitting layer or the light emitting material, preventtransfer of excitons formed in the light emitting layer to the holeinjecting layer and have the excellent ability of forming a thin film,are preferable. Examples of the electron injecting compound includefluorenone, anthraquinodimethane, diphenoquinone, thiopyrane dioxide,oxazoles, oxadiazoles, triazoles, imidazoles, perylenetetracarboxylicacid, quinoxaline, fluorenylidenemethane, anthraquinodimethane, anthroneand derivatives of these compounds. However, the electron injectingmaterial is not limited to these compounds.

Among these electron injecting materials, the more effective electroninjecting materials are metal complex compounds and five-memberedderivatives having nitrogen atom. Examples of the metal complex compoundinclude 8-hydroxyquinolinatolithium, bis(8-hydroxyquinolinato)zinc,bis(8-hydroxyquinolinato)copper, bis(8-hydroxyquinolinato)manganese,tris(8-hydroxyquinolinato)aluminum,tris(2-methyl-8-hydroxyquinolinato)aluminum,tris(8-hydroxyquinolinato)-gallium,bis(10-hydroxybenzo[h]quinolinato)beryllium,bis(10-hydroxy-benzo[h]quinolinato)zinc,bis(2-methyl-8-quinolinato)chlorogallium,bis(2-methyl-8-quinolinato)(o-cresolato) gallium,bis(2-methyl-8-quinolinato)-(1-naphtholato)aluminum andbis(2-methyl-8-quinolinato)(2-naphtholato)-gallium. However the electroninjecting material is not limited to these compounds.

As the five-membered derivative having nitrogen atom, oxazoles,thiazoles, oxadiazoles, thiadiazoles, triazoles and derivatives of thesecompounds are preferable. Examples of the five-membered derivativehaving nitrogen atom include 2,5-bis(1-phenyl)-1,3,4-oxazole,dimethylPOPOP, 2,5-bis(1-phenyl)-1,3,4-thiazole,2,5-bis(1-phenyl)-1,3,4-oxadiazole,2-(4′-tert-butylphenyl)-5-(4″-biphenyl)-1,3,4-oxadiazole,2,5-bis(1-naphthyl)-1,3,4-oxadiazole,1,4-bis[2-(5-phenyloxadiazolyl)]benzene,1,4-bis[2-(5-phenyloxadiazolyl)-4-tert-butylbenzene],2-(4′-tert-butyl-phenyl)-5-(4″-biphenyl)-1,3,4-thiadiazole,2,5-bis(1-naphthyl)-1,3,4-thiadiazole,1,4-bis[2-(5-phenylthiadiazolyl)]benzene,2-(4′-tert-butyl-phenyl)-5-(4″-biphenyl)-1,3,4-triazole,2,5-bis(1-naphthyl)-1,3,4-triazole and1,4-bis[2-(5-phenyltriazolyl)]benzene. However, the five-memberedderivative having nitrogen atom is not limited to these compounds.

The property of charge injection can be improved by adding anelectron-accepting compound to the hole injecting material and anelectron-donating compound to the electron injecting material.

As the electrically conductive material used for the anode of theorganic EL device of the present invention, a material having a workfunction greater than 4 eV is suitable, and carbon, aluminum, vanadium,iron, cobalt, nickel, tungsten, silver, gold, platinum, palladium,alloys of these metals, metal oxides such as tin oxides and indium oxideused for ITO substrates and NESA substrates and organic electricallyconductive resins such as polythiophene and polypyrrol are used. As theelectrically conductive material used for the cathode, a material havinga work function smaller than 4 eV is suitable, and magnesium, calcium,tin, lead, titanium, yttrium, lithium, ruthenium, manganese, aluminumand alloys of these metals are used. However, the electricallyconductive material used for the cathode is not limited to thesematerials. Typical examples of the alloy include magnesium/silver,magnesium/indium and lithium/aluminum. However, the alloy is not limitedto these alloys. The composition of the alloy is controlled by thetemperature of the source of vaporization, the atmosphere and the degreeof vacuum, and a suitable composition is selected. The anode and thecathode may be formed with a structure having two or more layers, wherenecessary.

The organic EL device of the present invention may comprise an inorganiccompound layer between at least one of the electrodes and the aboveorganic thin film layer. Examples of the inorganic compound used for theinorganic compound layer include various types of oxides, nitrides andoxide nitrides such as alkali metal oxides, alkaline earth metal oxides,rare earth oxides, alkali metal halides, alkaline earth metal halides,rare earth halides, SiO_(x), AlO_(x), SiN_(x), SiON, AlON, GeO_(x),LiO_(x), LiON, TiO_(x), TiON, TaO_(x), TaON, TaN_(x) and C. Inparticular, as the component contacting the anode, SiO_(x), AlO_(x),SiN_(x), SiON, AlON, GeO_(x) and C are preferable since a stableinterface layer of injection is formed. As the component contacting thecathode, LiF, MgF₂, CaF₂, MgF₂ and NaF are preferable.

In the organic EL device of the present invention, it is preferable thatat least one surface is sufficiently transparent in the region of thewavelength of the light emitted by the device so that the light emissionis achieved efficiently. It is preferable that the substrate is alsotransparent.

For the transparent electrode, the conditions in the vapor deposition orthe sputtering are set so that the prescribed transparency is surelyobtained using the above electrically conductive material. It ispreferable that the electrode of the light emitting surface has atransmittance of light of 10% or greater. The substrate is notparticularly limited as long as the substrate has the mechanical andthermal strength and is transparent. Examples of the substrate includeglass substrates and transparent films of resins. Examples of thetransparent film of a resin include films of polyethylene,ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers,polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride,polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketones,polysulfones, polyether sulfones, tetrafluoroethylene-perfluoroalkylvinyl ether copolymers, polyvinyl fluoride, tetrafluoroethylene-ethylenecopolymers, tetrafluoroethylene-hexafluoropropylene copolymers,polychlorotrifluoroethylene, polyvinylidene fluoride, polyesters,polycarbonates, polyurethanes, polyimides, polyether imides, polyimidesand polypropylene.

In the organic EL device of the present invention, it is possible that aprotective layer is formed on the surface of the device or the entiredevice is covered with silicone oil or a resin so that stability underthe effect of the temperature, the humidity and the atmosphere isimproved.

For the formation of each layer of the organic EL device of the presentinvention, any of the dry processes of film formation such as the vacuumvapor deposition, the sputtering, the plasma plating and the ion platingand the wet processes of film formation such as the spin coating, thedipping and the flow coating, can be conducted. The thickness of eachfilm is not particularly limited. However, it is necessary that thethickness of the film be set at a suitable value. When the thickness isexcessively great, application of a greater voltage is necessary toobtain the same output of the light, and the current efficiencydecreases. When the thickness is excessively small, pin holes areformed, and sufficient light emission cannot be obtained even when anelectric field is applied. In general, a thickness in the range of 5 nmto 10 μm is suitable and a thickness in the range of 10 nm to 0.2 μm ispreferable.

When the wet process of film formation is used, the material formingeach layer is dissolved or suspended in a suitable solvent such asethanol, chloroform, tetrahydrofuran and dioxane, and a thin film isformed from the obtained solution or suspension. Any of the abovesolvents can be used. For any of the layers, suitable resins andadditives may be used to improve the property for film formation and toprevent formation of pin holes in the film. Examples of the resin whichcan be used include insulating resins such as polystyrene,polycarbonates, polyarylates, polyesters, polyamides, polyurethanes,polysulfones, polymethyl methacrylate, polymethyl acrylate, celluloseand copolymer resins derived from these resins; photoconductive resinssuch as poly-N-vinylcarbazole and polysilanes; and electricallyconductive resins such as polythiophene and polypyrrol. Examples of theadditive include antioxidants, ultraviolet light absorbents andplasticizers.

As described above, by using the compound represented by general formula(1) for the organic thin film layer of the organic EL device of thepresent invention, the organic EL device emitting blue light with a highpurity of color can be obtained. This organic EL device can beadvantageously used for a photosensitive member for electronicphotograph, a planar light emitting member such as a flat panel displayof wall televisions, a back light of copiers, printers and liquidcrystal displays, a light source for instruments, a display panel, amarking light and an accessory.

The present invention will be described more specifically with referenceto examples in the following. However, the present invention is notlimited to the examples.

EXAMPLE

The triplet energy gap and the singlet energy of a compound weremeasured in accordance with the following methods.

(1) Measurement of the Triplet Energy

The lowest excited triplet energy level T1 was measured. Thephosphorescence spectrum of a sample was measured (a 10 μmoles/liter EPAsolution (diethyl ether:isopentane:ethanol=5:5:2 by volume); 77K; aquartz cell; FLUOROLOG II manufactured by SPEX Company). A tangent wasdrawn to the increasing line at the short wavelength side of thephosphorescence spectrum, and the wavelength (the end of light emission)at the intersection of the tangent and the abscissa was obtained. Theobtained wavelength was converted into the energy.

(2) Measurement of the Singlet Energy

The excited singlet energy was measured. Using a toluene solution (10⁻⁵moles/liter) of a sample, the absorption spectrum was obtained by aspectrometer for absorption of ultraviolet and visible lightmanufactured by HITACHI Co. Ltd. A tangent was drawn to the increasingline at the long wavelength side of the spectrum, and the wavelength(the end of absorption) at the intersection of the tangent and theabscissa was obtained. The obtained wavelength was converted into theenergy.

Synthesis Example 1 (Synthesis of Compound (1))

The route of synthesis of Compound (1) is shown in the following.

(1) Synthesis of Intermediate Product (A)

Into 300 ml of ethanol, 15.0 g (81 mmole) of 4-bromobenzaldehyde and 9.7g (81 mmole) of acetophenone were dissolved. To the resultant solution,16.6 ml (81 mmole) of a 28% solution of sodium methoxide in methanol wasadded, and the obtained mixture was stirred at the room temperature for9 hours. After the reaction was completed, the formed crystals wereseparated by filtration and washed with ethanol, and 19.6 g (the yield:84%) of intermediate product (A) was obtained.

(2) Synthesis of Intermediate Product (B)

Into 27 ml of acetic acid, 9.0 g (31 mmole) of intermediate product (A),8.7 g (31 mmole) of 1-phenacylpyridinium bromide and 19.3 g (250 mmole)of ammonium acetate were suspended, and the resultant suspension washeated under the refluxing condition for 12 hours. The reaction fluidwas cooled to the room temperature. Toluene and water were added to thefluid, and the resultant mixed fluid was separated into two layers. Theorganic layer was washed with a 10% aqueous solution of sodium hydroxideand a saturated aqueous solution of sodium chloride, successively, anddried with anhydrous sodium sulfate. After the organic solvent wasremoved by distillation under a reduced pressure, 27 ml of ethanol wasadded to the residue. The formed crystals were separated by filtrationand washed with ethanol, and 10.6 g (the yield: 88%) of intermediateproduct (B) was obtained.

(3) Synthesis of Compound (1)

Into 15 ml of toluene, 3.0 g (8 mmole) of intermediate product (B), 1.4g (8 mmole) of β-carboline, 0.18 g (0.2 mmole) oftris(dibenzylideneacetone)dipalladium, 0.23 g (0.6 mmole) of2-dicyclohexylphosphino-2′-(N,N-dimethylamino)biphenyl and 1.0 g (11mmole) of sodium tert-butoxide were suspended, and the resultantsuspension was heated under the refluxing condition for 20 hours underthe atmosphere of argon. The reaction fluid was cooled to the roomtemperature. Methylene chloride and water were added to the fluid, andthe resultant mixture was separated into two layers. The organic layerwas washed with water and dried with anhydrous sodium sulfate. After theorganic solvent was removed by distillation under a reduced pressure,the obtained residue was purified in accordance with the silica gelcolumn chromatography, and 1.7 g (the yield: 46%) of crystals wereobtained.

It was confirmed in accordance with 90 MHz ¹H-NMR and the fileddesorption mass spectroscopy (FD-MS) that the obtained crystals were theobject compound. The result of the measurement in accordance with FD-MSis shown in the following.

FD-MS calcd. for C₃₄H₂₃N₃=473; found: m/z=473 (M⁺, 100)

Synthesis Example 2 (Synthesis of Compound (2))

The route of synthesis of Compound (2) is shown in the following.

(1) Synthesis of Intermediate Product (C)

Into 75 ml of ethanol, 10.0 g (35 mmole) of intermediate product (A) and5.5 g (35 mmole) of benzamidine hydrochloride were suspended. To theresultant suspension, 2.8 g (70 mmole) of sodium hydroxide was added,and the resultant mixture was heated under the refluxing condition for18 hours. The reaction fluid was cooled to the room temperature. To thecooled fluid, 50 ml of water was added, and the resultant mixture wasstirred for 1 hour. The formed crystals were separated by filtration andwashed with ethanol, and 8.2 g (the yield: 61%) of intermediate product(C) was obtained.

(2) Synthesis of Compound (2)

In accordance with the same procedures as those conducted in SynthesisExample 1 except that intermediate product (C) was used in place ofintermediate product (B), 1.8 g (the yield: 45%) of crystals wereobtained.

It was confirmed in accordance with 90 MHz ¹H-NMR and FD-MS that theobtained crystals were the object compound. The result of themeasurement in accordance with FD-MS is shown in the following.

FD-MS calcd. for C₃₃H₂₂N₄=474; found: m/z=474 (M⁺, 100)

Synthesis Example 3 (Synthesis of Compound (61))

The route of synthesis of Compound (61) is shown in the following.

(1) Synthesis of Intermediate Product (D)

Into 60 ml of toluene, 25.4 g (90 mmole) of 4-bromoiodobenzene, 10.1 g(60 mmole) of β-carboline, 0.55 g (0.6 mmole) oftris(dibenzylideneacetone)dipalladium, 0.71 g (1.8 mmole) of2-dicyclohexylphosphino-2′-(N,N-dimethylamino)biphenyl and 8.1 g (84mmole) of sodium tert-butoxide were suspended, and the resultantsuspension was heated under the refluxing condition for 20 hours underthe atmosphere of argon. The reaction fluid was cooled to the roomtemperature. Water was added to the fluid, and the resultant mixture wasseparated into two layers. The organic layer was washed with water anddried with anhydrous sodium sulfate. After the organic solvent wasremoved by distillation under a reduced pressure, the obtained residuewas purified in accordance with the silica gel column chromatography,and 11.4 g (the yield: 59%) of crystals were obtained.

(2) Synthesis of Intermediate Product (E)

Into 50 ml of toluene and 50 ml of ether, 8.1 g (25 mmole) ofintermediate product (D) was dissolved. Under the atmosphere of argon,21 ml (32 mmole) of a hexane solution of n-butyllithium (1.6 M) wasadded to the resultant solution at −40° C., and the obtained solutionwas stirred at −40 to 0° C. for 1 hour. After the reaction solution wascooled to −70° C., a solution obtained by diluting 17 ml (74 mmole) oftriisopropyl borate with 25 ml of ether was added dropwise. After theresultant solution was stirred at −70° C. for 1 hour, the temperaturewas elevated to the room temperature, and the solution was stirred for 6hours. To the resultant reaction solution, 70 ml of a 5% hydrochloricacid was added dropwise, and the obtained solution was stirred at theroom temperature for 45 hours. The reaction solution was separated intotwo liquid layers, and the organic layer was washed with a saturatedaqueous solution of sodium chloride and dried with anhydrous sodiumsulfate. The organic solvent was removed by distillation under a reducedpressure until the amount of the organic solvent decreased to about onefifth of the original amount. The formed crystals were separated byfiltration and washed with a mixed solvent of toluene and n-hexane andn-hexane, successively, and 3.2 g (the yield: 45%) of intermediateproduct (E) was obtained.

(3) Synthesis of Compound (61)

Into 21 ml of 1,2-dimethoxyethane, 2.7 g (6.9 mmole) of intermediateproduct (C), 2.0 g (6.9 mmole) of intermediate product (E) and 0.16 g(0.14 mmole) of tetrakis-(triphenylphosphine)palladium were suspended.To the resultant suspension, a solution obtained by dissolving 2.2 g (21mmole) of sodium carbonate into 11 ml of water was added, and theobtained mixture was heated under the refluxing condition for 9 hours.After the reaction fluid was separated into two layers, the organiclayer was washed with a saturated solution of sodium chloride and driedwith anhydrous sodium sulfate. The organic solvent was removed bydistillation under a reduced pressure, and 12 ml of ethyl acetate wasadded to the residue. The formed crystals were separated by filtrationand washed with ethyl acetate, and 2.7 g (the yield: 72%) of crystalswere obtained.

It was confirmed in accordance with 90 MHz ¹H-NMR and FD-MS that theobtained crystals were the object compound. The result of themeasurement in accordance with FD-MS is shown in the following.

FD-MS calcd. for C₃₉H₂₆N₄=550; found: m/z=550 (M⁺, 100)

Synthesis Example 4 (Synthesis of Compound (68))

The route of synthesis of Compound (68) is shown in the following.

(1) Synthesis of Intermediate Product (F)

Into 210 ml of toluene, 7.9 g (84 mmole) of 4-aminopyridine, 25.0 g (88mmole) of 2-bromoiodobenzene, 1.5 g (1.6 mmole) oftris(dibenzylideneacetone)dipalladium, 1.8 g (3.2 mmole) of1,1′-bis-(diphenylphosphino)ferrocene and 11.3 g (118 mmole) of sodiumtert-butoxide were suspended, and the resultant suspension was heatedunder the refluxing condition for 19 hours under the atmosphere ofargon. The reaction solution was cooled to the room temperature. Afteradding water, the reaction solution was separated into two layers, andthe organic layer was washed with water and dried with anhydrous sodiumsulfate. The organic solvent was removed by distillation under a reducedpressure, and 50 ml of ethanol was added to the residue. The formedcrystals were separated by filtration and washed with ethanol, and 20.5g (the yield: 98%) of intermediate product (F) was obtained.

(2) Synthesis of Intermediate Product (G)

Into 80 ml of N,N-dimethylformamide, 10.0 g (40 mmole) of intermediateproduct (F), 0.90 g (4.0 mmole) of palladium acetate and 5.9 g (56mmole) of sodium carbonate were suspended, and the resultant suspensionwas heated under the refluxing condition for 18 hours. The reactionfluid was cooled to the room temperature. After adding ethyl acetate andwater, the reaction fluid was separated into two layers, and the organiclayer was washed with water and a saturated solution of sodium chloride,successively, and dried with anhydrous sodium sulfate. The organicsolvent was removed by distillation under a reduced pressure, and theresidue was recrystallized from toluene. The obtained crystals wereseparated by filtration and washed with toluene, and 4.4 g (the yield:66%) of intermediate product (G) was obtained.

(3) Synthesis of Intermediate Product (H)

Into 100 ml of ethanol, 15.0 g (54 mmole) of 2,4′-dibromo-acetophenoneand 5.2 g (55 mmole) of 2-aminopyridine were suspended. After 7.0 g (83mmole) of sodium hydrogencarbonate was added, the resultant suspensionwas heated under the refluxing condition for 9 hours. After the reactionfluid was cooled to the room temperature, the formed crystals wereseparated by filtration and washed with water and ethanol, successively,and 12.5 g (the yield: 85%) of intermediate product (H) was obtained.

(4) Synthesis of Compound (68)

In accordance with the same procedures as those conducted in SynthesisExample 1 (3) described above except that intermediate product (H) ofsynthesis was used in place of intermediate product (B) and intermediateproduct (G) was used in place of β-carboline, 1.8 g (the yield: 49%) ofcrystals were obtained.

It was confirmed in accordance with 90 MHz ¹H-NMR and FD-MS that theobtained crystals were the object compound. The result of themeasurement in accordance with FD-MS is shown in the following.

FD-MS calcd. for C₂₄H₁₅N₄=360; found: m/z=360 (M⁺, 100)

Synthesis Example 5 (Synthesis of Compound (72))

The route of synthesis of Compound (72) is shown in the following.

(1) Synthesis of Intermediate Product (I)

Into 100 ml of ethanol, 5.0 g (22 mmole) of 4-bromophenylhydrazinehydrochloride and 1.9 g (22 mmole) of sodium hydrogencarbonate weresuspended. After the resultant suspension was stirred for 1 hour, 2 ml(23 mmole) of concentrated hydrochloric acid was added, and theresultant mixture was heated under the refluxing condition for 8 hours.Then, 2 ml (23 mmole) of concentrated hydrochloric acid was added, andthe obtained mixture was heated under the refluxing condition for 12hours. After the reaction fluid was cooled to the room temperature, 2.3ml (23 mmole) of a 30% aqueous solution of sodium hydroxide and 50 ml ofwater were added, and the resultant mixture was stirred for 1 hour. Theformed crystals were separated by filtration and washed with ethanol,and 7.6 g (the yield: quantitative) of intermediate product (I) wasobtained.

(2) Synthesis of Compound (72)

In accordance with the same procedures as those conducted in SynthesisExample 1 (3) described above except that intermediate product (I) wasused in place of intermediate product (B), 1.8 g (the yield: 46%) ofcrystals were obtained.

It was confirmed in accordance with 90 MHz ¹H-NMR and FD-MS that theobtained crystals were the object compound. The result of themeasurement in accordance with FD-MS is shown in the following.

FD-MS calcd. for C₃₂H₂₂N₄=462; found: m/z=462 (M⁺, 100)

Synthesis Example 6 (Synthesis of Compound (23))

The route of synthesis of Compound (23) is shown in the following.

Intermediate product (J) was synthesized in accordance with the sameprocedures as those conducted in Synthesis Examples 1 (1) and (2) exceptthat 3,5-dibromobenzaldehyde was used in place of 4-bromobenzaldehydeused in Synthesis Example 1 (1). Into 15 ml of toluene, 2.5 mg (5 mmole)of intermediate product (J), 1.0 g (6 mmole) of β-carboline, 0.18 g (0.2mmole) of tris(dibenzylideneacetone)-dipalladium, 0.23 g (0.6 mmole) of2-dicyclohexylphosphino-2′-(N,N-dimethylamino)biphenyl and 1.0 g (11mmole) of sodium tert-butoxide were suspended, and the resultantsuspension was heated under the refluxing condition for 20 hours underthe atmosphere of argon. After the reaction fluid was cooled to the roomtemperature, methylene chloride and water were added to the reactionfluid. The obtained fluid was separated into two layers, and the organiclayer was washed with water and dried with anhydrous sodium sulfate.After the organic solvent was removed by distillation under a reducedpressure, the residue of distillation was suspended into 15 ml oftoluene. To the obtained suspension, 0.18 g (0.2 mmole) oftris(dibenzylideneacetone)dipalladium, 0.23 g (0.6 mmole) of2-dicyclohexylphosphino-2′-(N,N-dimethylamino)-biphenyl and 1.0 g (11mmole) of sodium tert-butoxide were added, and the resultant mixture washeated under the refluxing condition for 20 hours under the atmosphereof argon. After the reaction fluid was cooled to the room temperature,methylene chloride and water were added. The obtained fluid wasseparated into two layers, and the organic layer was washed with waterand dried with anhydrous sodium sulfate. After the organic solvent wasremoved by distillation under a reduced pressure, the residue waspurified in accordance with the silica gel column chromatography, and1.7 g (the yield: 53%) of crystals were obtained.

It was confirmed in accordance with 90 MHz ¹H-NMR and FD-MS that theobtained crystals were the object compound. The result of themeasurement in accordance with FD-MS is shown in the following.

FD-MS calcd. for C₄₅H₂₀N₄=639; found: m/z=639 (M⁺, 100)

Example 1 (Preparation of an Organic EL Device)

A glass substrate (manufactured by GEOMATEC Company) of 25 mm×75 mm×0.7mm thickness having an ITO transparent electrode was cleaned byapplication of ultrasonic wave in isopropyl alcohol for 5 minutes andthen by exposure to ozone generated by ultraviolet light for 30 minutes.The glass substrate having the transparent electrode which had beencleaned was attached to a substrate holder of a vacuum vapor depositionapparatus. On the surface of the cleaned substrate at the side havingthe transparent electrode, a film of copper phthalocyanine (referred toas “CuPc film”, hereinafter) having a thickness of 10 nm was formed in amanner such that the formed film covered the transparent electrode. Theformed CuPc film worked as the hole injecting layer. On the formed CuPcfilm, a film of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl shownbelow (referred to as “α-NPD film”, hereinafter) having a thickness of30 nm was formed. The formed α-NPD film worked as the hole transportinglayer. On the formed α-NPD film, a film of Compound (1) prepared abovehaving a thickness of 30 nm was formed by vapor deposition usingCompound (1) as the host material, and the light emitting layer wasformed. At the same time, tris(2-phenylpyridine)Ir shown below (referredto as “Ir(ppy)₃”, hereinafter) was added as the Ir metal complexemitting phosphorescent light. The content of Ir(ppy)₃ in the lightemitting layer was 5% by weight. This film worked as the light emittinglayer. On the film formed above, a film of(1,1′-bisphenyl)-4-olato)bis(2-methyl-8-quinolinolato)aluminum shownbelow (referred to as “BAlq film”, hereinafter) having a thickness of 10nm was formed. BAlq film worked as the hole barrier layer. On this film,a film of an aluminum complex of 8-hydroxyquinoline shown below(referred to as “Alq film”, hereinafter) having a thickness of 40 nm wasformed. Alq film worked as the electron injecting layer. Then, LiF whichis an alkali metal halide was vapor deposited to form a film having athickness of 0.2 nm. On the formed film, aluminum was vapor deposited toform a film having a thickness of 150 nm. The Al/LiF film worked as thecathode. An organic EL device was prepared in the manner describedabove.

The triplet energy and the singlet energy of the host material used inthe light emitting layer were measured in accordance with the methodsdescribed above in (1) and (2), respectively. The results are shown inTable 1.

The device prepared above was examined by passing electric current.Green light was emitted at a luminance of 99 cd/m² under a voltage of5.2 V and a current density of 0.26 mA/cm². The chromaticity coordinateswere (0.32, 0.62), and the current efficiency was 38.6 cd/A. Theseresults are shown in Table 1.

Examples 2 and 3

Organic EL devices were prepared in accordance with the same proceduresas those conducted in Example 1 except that compounds shown in Table 1were used in place of Compound (1), and the triplet energy, the singletenergy, the voltage, the current density, the luminance, the currentefficiency and the chromaticity were measured in accordance with thesame methods as those conducted in Example 1. The results are shown inTable 1.

Comparative Example 1

An organic EL device was prepared in accordance with the same proceduresas those conducted in Example 1 except that compound (BCz) shown in thefollowing was used in place of Compound (1), and the triplet energy, thesinglet energy, the voltage, the current density, the luminance, thecurrent efficiency and the chromaticity were measured in accordance withthe same methods as those conducted in Example 1. The results are shownin Table 1.

Comparative Example 2

An organic EL device was prepared in accordance with the same proceduresas those conducted in Example 1 except that compound (A-10) shown in thefollowing, which is described in the specification of the United StatesPatent Application Publication No. 2002-28329, was used in place ofCompound (1), and the properties were measured in accordance with thesame methods as those conducted in Example 1. The results are shown inTable 1. TABLE 1-1 A-10

Host material Triplet Singlet Current of light energy energy Voltagedensity emitting layer (eV) (eV) (V) (mA/cm²) Example 1  (1) 2.8 3.4 5.20.26 Example 2 (61) 2.6 3.3 5.5 0.24 Example 3 (68) 2.7 3.5 5.6 0.27Comparative (BCz) 2.8 3.6 5.4 0.31 Example 1 Comparative (A-10) 3.1 3.75.9 0.32 Example 2

TABLE 1-2 Current Chromaticity Color of Luminance efficiency coordinatesemitted (cd/m²) (cd/A) (x, y) light Example 1 99 38.6 (0.32, 0.62) greenExample 2 102 42.8 (0.32, 0.61) green Example 3 100 37.2 (0.32, 0.61)green Comparative 101 32.6 (0.32, 0.61) green Example 1 Comparative 10031.8 (0.32, 0.61) green Example 2

As shown in Table 1, the organic EL devices using the material fororganic EL devices of the present invention emitted green light withgreater efficiencies than those of devices of Comparative Examples 1 and2 in which conventional compounds (BCz and A-10, respectively) wereused. Since the material for organic EL devices of the present inventionhad a great energy gap, the light emitting molecule having a greatenergy gap could be mixed into the light emitting layer and used for thelight emission.

Example 4

A glass substrate (manufactured by GEOMATEC Company) of 25 mm×75 mm×0.7mm thickness having an ITO transparent electrode was cleaned byapplication of ultrasonic wave in isopropyl alcohol for 5 minutes andthen by exposure to ozone generated by ultraviolet light for 30 minutes.The glass substrate having the transparent electrode which had beencleaned was attached to a substrate holder of a vacuum vapor depositionapparatus. On the surface of the cleaned substrate at the side havingthe transparent electrode, CuPc film having a thickness of 10 nm wasformed in a manner such that the formed film covered the transparentelectrode. The formed CuPc film worked as the hole injecting layer. Onthe formed CuPc film, a film of1,1′-bis[4-N,N-di(para-tolyl)aminophenyl]cyclohexane shown below(referred to as “TPAC film”, hereinafter) having a thickness of 30 nmwas formed. The formed TPAC film worked as the hole transporting layer.On the formed TPAC film, a film of Compound (1) prepared above having athickness of 30 nm was formed by vapor deposition, and the lightemitting layer was formed. At the same time, Irbis[(4,6-difluorophenyl)pyridinato-N,C²]picolinate shown below (referredto as “FIrpic”, hereinafter) was added as the Ir metal complex emittingphosphorescent light. The content of FIrpic in the light emitting layerwas 7% by weight. This film worked as the light emitting layer. On thefilm formed above, Alq film having a thickness of 30 nm was formed. Alqfilm worked as the electron injecting layer. Then, LiF which is analkali metal halide was vapor deposited to form a film having athickness of 0.2 nm. On the formed film, aluminum was vapor deposited toform a film having a thickness of 150 nm. The Al/LiF film worked as thecathode. An organic EL device was prepared in the manner describedabove.

The triplet energy and the singlet energy of the host material used inthe light emitting layer were measured in accordance with the methodsdescribed above in (1) and (2), respectively. The results are shown inTable 2.

The device prepared above was examined by passing electric current. Bluelight was emitted at a luminance of 101 cd/m² under a voltage of 6.4 Vand a current density of 0.65 mA/cm². The chromaticity coordinates were(0.17, 0.39), and the current efficiency was 15.6 cd/A.

Examples 5 and 6

Organic EL devices were prepared in accordance with the same proceduresas those conducted in Example 4 except that compounds shown in Table 2were used in place of Compound (1), and the triplet energy, the singletenergy, the voltage, the current density, the luminance, the currentefficiency and the chromaticity were measured in accordance with thesame methods as those conducted in Example 2. The results are shown inTable 2.

Comparative Example 3

An organic EL device was prepared in accordance with the same proceduresas those conducted in Example 4 except that compound (BCz) shown abovewas used in place of Compound (1), and the triplet energy, the singletenergy, the voltage, the current density, the luminance, the currentefficiency and the chromaticity were measured in accordance with thesame methods as those conducted in Example 4. The results are shown inTable 2.

Comparative Example 4

An organic EL device was prepared in accordance with the same proceduresas those conducted in Comparative Example 3 except that compound (α-NPD)shown above was used for the hole transporting layer in place of TPACand compound (BAlq) shown above was used for the electron injectinglayer in place of compound (Alq). The triplet energy, the singletenergy, the voltage, the current density, the luminance, the currentefficiency and the chromaticity were measured in accordance with thesame methods. The results are shown in Table 2. TABLE 2 - 1 Hostmaterial Triplet Singlet Current of light energy energy Voltage densityemitting layer (eV) (eV) (V) (mA/cm²) Example 4 (1) 2.8 3.4 6.4 0.65Example 5 (2) 2.8 3.4 6.8 0.57 Example 6 (3) 2.7 3.2 6.9 0.73Comparative (BCz) 2.8 3.6 7.8 1.70 Example 3 Comparative (BCz) 2.8 3.67.6 1.09 Example 4

TABLE 2-2 Chromaticity Current coordinates Luminance efficiency lightColor of (cd/m²) (cd/A) (x, y) emitted Example 4 101 15.6 (0.17, 0.39)blue Example 5 103 18.2 (0.18, 0.39) blue Example 6 97 13.3 (0.18, 0.39)blue Comparative 98 5.8 (0.16, 0.37) blue Example 3 Comparative 99 9.2(0.17, 0.37) blue Example 4

As shown in Table 2, the organic EL devices using the material fororganic EL devices of the present invention could be driven under alower voltage and emitted blue light with greater efficiencies thanthose of devices of Comparative Example 3 and 4 in which conventionalcompound (BCz) was used. Since the material for organic EL devices ofthe present invention had a great energy gap, the light emittingmolecule having a great energy gap could be mixed into the lightemitting layer and used for the light emission.

INDUSTRIAL APPLICABILITY

As described specifically in the above, the organic EL device whichemits light under a low voltage with a greater current efficiency byutilizing the emission of phosphorescent light can be obtained when thematerial for organic EL devices of the present invention comprising thecompound represented by general formula (1) is used. Therefore, theorganic EL device of the present invention is very useful forapplications such as light sources of various electronic instruments.

1. A material for organic electroluminescence devices which comprises acompound represented by following general formula (1):

wherein X₁ to X₈ each represent carbon atom or nitrogen atom, and atleast one of X₁ to X₈ represents nitrogen atom; when any of X₁ to X₈represent carbon atom, R₁ to R₈ connected to X₁ to X₈ representingcarbon atom, respectively, each represent a substituent bonded to thecarbon atom; adjacent substituents represented by R₁ to R₈ may form aring; when any of X₁ to X₈ represent nitrogen atom, R₁ to R₈ connectedto X₁ to X₈ representing nitrogen atom, respectively, each represent anoncovalent electron pair; and R₉ represents a substituent.
 2. Amaterial for organic electroluminescence devices according to claim 1,wherein R₁ to R₉ each represent -L or -L-Y, wherein L representshydrogen atom, a substituted or unsubstituted aryl group having 6 to 40carbon atoms, a substituted or unsubstituted heterocyclic group having 2to 40 carbon atoms, a substituted or unsubstituted linear or branchedalkyl group having 1 to 20 carbon atoms, a substituted or unsubstitutedcycloalkyl group having 6 to 40 carbon atoms, a substituted orunsubstituted amino group having 2 to 40 carbon atoms, a substituted orunsubstituted linear or branched alkoxyl group having 1 to 40 carbonatoms, a halogen atom, nitro group, a substituted or unsubstitutedarylene group having 6 to 40 carbon atoms, a substituted orunsubstituted divalent heterocyclic group having 2 to 40 carbon atoms, alinear or branched substituted or unsubstituted alkylene group having 1to 20 carbon atoms or a substituted or unsubstituted cycloalkylene grouphaving 6 to 40 carbon atoms; and Y represents hydrogen atom, asubstituted or unsubstituted aryl group having 6 to 40 carbon atoms, asubstituted or unsubstituted heterocyclic group having 2 to 40 carbonatoms, a substituted or unsubstituted linear or branched alkyl grouphaving 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkylgroup having 6 to 40 carbon atoms, a substituted or unsubstituted aminogroup having 2 to 40 carbon atoms, a substituted or unsubstituted linearor branched alkoxyl group having 1 to 40 carbon atoms, a halogen atom ornitro group.
 3. A material for organic electroluminescence devicesaccording to claim 1, wherein one to three among X₁ to X₈ each representnitrogen atom, and the others each represent carbon atom.
 4. A materialfor organic electroluminescence devices according to claim 1, wherein atleast one of X₃ and X₆ among X₁ to X₈ represents nitrogen atom, and theothers each represent carbon atom.
 5. A material for organicelectroluminescence devices according to claim 1, wherein at least oneof R₁ to R₈ represents β-carbolinyl group.
 6. A material for organicelectroluminescence devices according to claim 2, wherein at least oneof L and Y represents β-carbolinyl group.
 7. A material for organicelectroluminescence devices according to claim 1, wherein an energy gapof a triplet state is 2.5 to 3.3 eV.
 8. A material for organicelectroluminescence devices according to claim 1, wherein an energy gapof a singlet state is 2.8 to 3.8 eV.
 9. An organic electroluminescencedevice comprising a cathode, an anode and an organic thin film layerwhich is sandwiched between the cathode and the anode and comprises atleast one layer, wherein at least one layer in the organic thin filmlayer contains a material for organic electroluminescence devicesdescribed in claim
 1. 10. An organic electroluminescence devicecomprising a cathode, an anode and an organic thin film layer which issandwiched between the cathode and the anode and comprises at least onelayer, wherein a light emitting layer contains a material for organicelectroluminescence devices described in claim
 1. 11. An organicelectroluminescence device comprising a cathode, an anode and an organicthin film layer which is sandwiched between the cathode and the anodeand comprises at least one layer, wherein at least one of an electrontransporting layer and an electron injecting layer contains a materialfor organic electroluminescence devices described in claim
 1. 12. Anorganic electroluminescence device comprising a cathode, an anode and anorganic thin film layer which is sandwiched between the cathode and theanode and comprises at least one layer, wherein at least one of a holetransporting layer and a hole injecting layer contains a material fororganic electroluminescence devices described in claim
 1. 13. An organicelectroluminescence device according to claim 9, wherein the materialfor organic electroluminescence devices is an organic host material. 14.An organic electroluminescence device according to claim 9, whichcomprises an inorganic compound layer sandwiched between at least one ofthe electrodes and the organic thin film layer.
 15. An organicelectroluminescence device according to claim 9, wherein the organicthin film layer contains a phosphorescent emissive compound.
 16. Anorganic electroluminescence device according to claim 9, which emitsbluish light.